This invention relates to a contact arrangement for vacuum switches in general and more particularly to a contact arrangement with cup contacts having improved arc stabilization.
A contact arrangement for vacuum switches with cup contacts which are arranged coaxially with respect to each other and the slotted contact carrier of which is provided with a closed contact ring, the end face of which forms the contact surface is known in the art.
The cup contacts, which are coaxially disposed opposite each other, each form a hollow body of revolution, the bottom of which is connected to a current lead and the rim of which forms the annular contact surface. The contact carriers of both contacts are provided with inclined slots arranged in opposite directions, which divide the contact carrier into individual segments. These segments, together with the arc drawn after the contacts are opened, form a current loop, the Lorentz force of which makes the arc rotate between the contacts. The inclination of the slots relative to the axis of the cup contact is chosen large enough so that the slots overlap in the contact carrier in the azimuthal direction. The bottom of the cup contact can also be provided with slots (German Pat. No. 1 196 751).
One known embodiment of a contact arrangement for vacuum switches contains cup contacts which are provided with a washer-like contact overlay. The two contacts are arranged concentrically to each other in such a manner that an inner contact is surrounded by the contact walls of the outer contact and their rims point axially in the same direction. In the case of the outer contact, the contact overlay is arranged inside the cup, while in the case of the inner contact, the current lead is arranged in the cup and the bottom of the contact is provided with the contact overlay. The contact overlays are therefore opposite each other in a central part of the two contacts. An arc drawn after the contacts are lifted is to be driven away from the contact surfaces toward the walls of the cup contacts, which serve as burn-off areas of the contacts. To accomplish this, a flat intermediate layer of a material having a higher electric resistance is embedded between the respective contact overlay and the current lead, and is arranged as close to the current lead as possible in the bottom of the cup contacts (German Offenlegungsschrift No. 25 46 376).
It is now an object of the present invention to force, in a contact arrangement with cup contacts, the rims of which form the respective contact surfaces, a current distribution in each of the contacts, between the current leads and the annular contact surface, such that the bases of a rotating arc drawn between the contacts are stabilized between the contact surfaces. In particular, a force component on the arc directed radially inward as well as outward is to be avoided.